The United States relies on imported petroleum to meet the needs of transportation fuel. To reduce dependence on the imported petroleum, the Environmental Protection Agency (EPA) set standards for a Renewable Fuel Standard (RFS2) program each year. See, United States Environmental Protection Agency, Office of Transportation and Air Quality, “EPA Proposes 2014 Renewable Fuel Standards, 2015 Biomass -Based Diesel Volume,” November 2013 Regulatory Announcement. The RFS2 includes a mandate to blend renewable fuels into transportation fuel, which ensures the continued growth of renewable fuels. The RFS2proposes annual standards for cellulosic biofuel, biomass-based diesel, advanced biofuel, and total renewable fuel that apply to gasoline and diesel. The proposal is 17 million gallons of cellulosic biofuels, 1.28 billion gallons of biomass-based diesel, 2.0-2.5 billion gallons of advanced biofuel, and 15-15.5 billion gallons of renewable fuel to be produced and for consumption in 2014.
Meanwhile, efforts have been undergoing to reduce travel demand, to improve vehicle efficiency, and to switch to cleaner, lower-carbon fuels. These efforts have focused on establishing a national low carbon fuel standard (LCFS) together, or in place of the RFS2. The LCFS includes all types of transporatation fuels (i.e., electricity, natural gas, hydogen, and biofuels), requires reducing a fuel's average life-cycle gas house gas (GHG) emissions or carbon-intensity (CI) over a certain period of time, and stimulates innovation by rewarding production facilities that reduce GHG or carbon emissions at every step. Production facilities can reduce CI of fuels by selling more low-carbon fuels, reducing the CI of fossil fuels, improving efficiencies, reducing carbon footprints, capturing and sequesting carbon, and/or purchasing credits from other producers who are able to supply low-carbon fuels at lower prices. California and some countries have adopted the LCFS policy. Other states and regions in the U.S. are considering adopting a LCFS policy similar to California's model.
A national LCFS would affect the economy and environment. These effects may be based on cost and availability of low-carbon fuels, GHG timeline reduction, and creation of a credit system. Advantages of incorporating LCFS to RFS2 are to reduce transportation fuel consumption and lower fuel prices, lower crop prices by shifting towarding cellulosic feedstocks, and reduce GHG or carbon emmisions significantly domestically and globablly. Thus, production facilities are seeking ways to implement LCFS on their own.
Since production facilities produce emissions, methods to implement LCFS include finding more efficient technologies. For instance, there are known techniques to separate solids from liquids in process streams. However, these techniques are not very efficient. For instance, one method uses heat and/or a centrifuge with the process streams to separate and to recover various components. Problems are that the centrifuge may not separate components, based on density differential and may not adequately separate solids from liquids in the process streams, is expensive to purchase and to operate, requires frequent maintenance and repair, and requires a higher skill set to operate and to maintain. Also, the solids have high moisture content, which drives up operating costs to transport and to dry the solids downstream. Plus, these pieces of equipment create emissions from the plants. Other types of equipment have been attempted for solids-liquids separation, but tend to drive up capital and operating costs.
Accordingly, there is a need for improved methods for optimization of dewatering insoluble solids in a more efficient manner by reducing GHG or carbon emissions, decreasing the amount of energy used for downstream processing, reducing operating costs, and/or reducing capital costs.